The NFL preseason still has a few days left. The 2016 presidential preseason still has a few months left — for every candidate but Hillary Clinton.

For Clinton, familiar to Americans as first lady, senator from New York and secretary of state, there is no preseason. She's been at the center of American attention for almost a quarter-century.

No American woman in our history has been so prominent for so long, with the possible exception of Eleanor Roosevelt, who was in the public eye for 29 years but who held no elected office. Susan B. Anthony was involved in women's issues for 55 years, but for many of those years operated beyond widespread attention. Frances Perkins served as labor secretary throughout the FDR administration — one of only two Roosevelt cabinet members to do so — and into the Truman administration but, apart from serving on the Civil Service Commission, largely faded from view afterward.

Clinton has not faded — indeed her national profile has only become more vivid — since she stood beside Bill Clinton 23 years ago this fall as he announced his candidacy for the White House. Every statement she utters makes news. She doesn't get to try out her lines in private, or before 18 people without cellphone cameras in the lobby of the Hotel Ottumwa 75 miles downstream from Des Moines, the way her putative rivals do.

It's a great advantage — and a great disadvantage.

The advantage is that she is by far the front-runner for the Democratic presidential nomination, with a position more commanding than any non-incumbent candidate — at least since Walter F. Mondale in 1984, perhaps since Adlai Stevenson in 1956. She will have money at hand and attention wherever she goes. For the next several months, her very presence — as a candidate if she becomes one, as a professed non-candidate until she withdraws — keeps others from the race and dollars from potential rivals.

The disadvantage is that when she says she and her husband were dead broke when they left the White House, or when she appears to seek distance from President Barack Obama and then appears to try to close the gap, she does so in the full glare of the public spotlight.

All that helps explain a very curious wrinkle in public opinion polling that is evident in the latest survey from the well-regarded Marist College Institute for Public Opinion.

That survey shows Clinton in two completely unremarkable positions: supported ardently by Democrats, opposed virulently by Republicans. In other years, important political figures have had performances that did not merit the adverbs (ardently, virulently) and thus have had cross-party appeals. But there is less of anything that appears across party lines today, so maybe the importance of that is smaller than it might otherwise appear.

The Marist survey shows Clinton defeating former Gov. Jeb Bush of Florida by seven percentage points and Gov. Chris Christie of New Jersey and Sen. Rand Paul of Kentucky by six points. These are relatively small margins, especially this early in the political cycle, especially since there breathes hardly a soul over 18 who has never heard of Clinton while the other three could walk undisturbed through just about any shopping mall in America outside their own states — and a few inside their home states.

But that is not what should be worrisome to Clinton's strategists.

This is: Her support among independent voters — who count in some primary states but not all, but who are potentially decisive in general elections — declined against each of those potential rivals. Indeed, that margin has declined by 10 points against Bush and nine against Paul.

"She's upped her visibility with her book tour and some of her misstatements, and that has shaken loose a few independents," explains Lee M. Miringoff, who directs the Marist poll. "For a while, the idea of her as a presidential candidate was abstract. Now people are getting a taste for what a second Hillary candidacy might be like."

That first campaign — a pioneering effort by a female candidate — was upended by the kind of inflexibility that did not allow for the entrant of another pioneer, the first mainstream black candidate, or for the importance of caucus states, which Obama focused on.

Clinton's 2008 campaign is regarded as an astonishing series of missed opportunities and squandered potential.

Mondale's presence in the 1984 race, for example, did not chill others from becoming presidential candidates the way Clinton's presence has.

Sen. John H. Glenn Jr. of Ohio jumped in the race, and for a while he presented an important challenge to the former vice president. Sen. Gary Hart of Colorado entered the contest, and though he operated below the political radar for many months, he emerged a winner in New Hampshire and nearly won the nomination.

In the unusual circumstances of 2016, political professionals are trying to measure just how effective a candidate Clinton can be in a race that appears to offer her a clear field, a situation much different from 1984.

She has every element — an organized, disciplined mind, a broad network of potential appointees, comprehensive knowledge of the world and familiarity with world leaders — of being a good president. In that regard, she has a profile much like that of George H.W. Bush.

But she might have another characteristic attributed to the elder Bush. She may be a superb potential president but an awkward, perhaps even halting, candidate. The problem with American politics since the beginning of the 20th century is that the qualities that make a political figure a good campaigner do not necessarily make him or her a good president.

Clinton can take some comfort from the notion that as the lone contender in the Democratic presidential race, all of her moves, especially missteps, prompt an outsized reaction. Right now the campaign is akin to walking on heels across concrete in an empty room. Once other candidates are in the race — and some surely will join — that room will have some carpeting and it will no longer be empty.

Even so, the perils of tripping are greater for her than for any other candidate. That's the price of being on top.

David Shribman, a Pulitzer Prize winner in journalism, is executive editor of the Pittsburgh Post-Gazette.